Originally, cells and membranes of living bodies are consisted of glycolipids, and accordingly the glycolipids present rich in amount on cellular surface and intercellular spaces and have a function of maintaining the intercellular bonding ability and the water-retaining ability of intercellular liquid by the hydrogen bond of the hydroxyl groups of the saccharide residue.
From the above-mentioned viewpoint, several applications are expected on the high polymeric substances having saccharide residues on their side chains and having a similar constitution to the glycolipids constituting the cells on account of their excellent hydrophilia and bio-adaptability as a high polymeric material having several functions for medical treatment.
However, the reports on the synthesis of high polymeric substances having saccharide residues on their side chains are unexpectedly small in number except for a report of Nishio et al. (Preliminary texts for XXIV Annual Meeting of High Polymer Soc. Japan, page 197 (1975) and that of Black et al. (J. Chem. Soc., 4433 (1963).
In the report by Nishio, a method for producing the compounds represented by the following formula (A) is disclosed: ##STR2## wherein acetobromoglucose is bonded by Koning's reaction to 2-hydroxyethyl methacrylate and the thus obtained monomer is polymerized and then the polymer is de-acetylated to obtain the high polymeric substance in which 1-position of the saccharide residue has an ether bonding to the main chain of the methacrylate.
On the other hand, Black et al. reported poly(3-O-methacroyl-D-glucose) represented by the following formula (B): ##STR3## obtained by at first acylating the hydroxyl group of 3-position of 1,2,5,6-diisopropylideneglucose, polymerizing the thus obtained monomer and de-acetylating the thus obtained polymer following the reaction formulae shown above.
Although the method of Nishio utilizes the Konig's reaction which is a conventional method of synthesizing a sugar ether for obtaining his monomer, it is said to be a laboratory-wise method from the view point of yield of the reaction.
On the other hand, the method of Black et al. is to obtain a high polymeric substance in which 3-position of the saccharide residue is acyl-bonded to the main chain and in this case, a selective protection of the other hydroxyl group is necessary. However, the protection of hydroxyl groups of the sugar is impossible in disaccharides and trisaccharides even if it is easily performed in a monosaccharide. Accordingly, the method of Black et al. cannot afford to give a high polymeric substance in which 3-position of polysaccharide residue is bonded to the side chain of the high polymer.
The present inventor from the consideration of the above-mentioned technical background and of the fact that the physical properties and the functions of the high polymeric substance having saccharide-bonded side chains in living bodies are variable corresponding to the kinds of saccharide and the position of bonding or the degree of polymerization, has tried to synthesize a high polymeric substance having a novel saccharide-bonded side chains. As a result the inventor has been successful in providing a novel high polymeric substance excellent in bio-adaptability.
The inventor could furnish high polymeric substances having saccharide molecules of various chain length in side chain by a sequence of reactions as follows:
At first, acrylic acid, methacrylic acid or one of their metal salts is made to react with a compound of sugar in which 1-position is activated by halogenation or orthoesterification and other hydroxyl groups are acylated to obtain a monomeric sugar acrylate or sugar methacrylate in which 1-position of the sugar is acrylated or methacrylated. Then the monomeric ester is polymerized and the polymer is de-acrylated by sodium methylate, ammonia, etc. Or, at first, a polymer of acrylic acid or methacrylic acid is made to react with a sugar having its 1-position selectively activated and then the product is de-acylated to obtain the end product.